Apparatus for working materials by means of an electron beam



Dec. 7, 1965 R. w. WINDEBANK 3,222,496

APPARATUS FOR WORKING MATERIALS BY MEANS OF AN ELECTRON BEAM Filed April4, 1963 F/GZ g I l W za .1 22

F/Gl5 l ROEERT W. WM/OEBA NK .38

ATTORNEK United States Patent 3,222,496 APPARATUS FOR WORKING MATERIALSBY MEANS OF AN ELECTRON BEAM Robert W. Windebank, Middlesex, England,assignor to International Resistance Company, Philadelphia, Pa. FiledApr. 4, 1963, Ser. No. 270,728 Claims priority, application GreatBritain, Apr. 18, 1962, 15,112/ 62 4 Claims. (Cl. 219-121) Thisinvention relates to apparatus for working materials by means of anelectron beam and is more particularly, although not necessarilyexclusively, concerned with the cutting of a metal layer carried upon asuitable substrate by a sharply fo-cussed electron beam under vacuo.

Among the objects of the invention are the provision of improvedarrangements for inserting and removing workpieces into and from theevacuated working zone, for reducing the amount of beam energy requiredto effect a given cutting or other working operation, for reducing thelocalised heating effects upon the substrate caused by the beam cuttingor other working operation, for annealing the workpiece during and afterthe working operation, and for providing a sharply focussed electronbeam of minimum cross-section. Other objects will appear hereinafter.

FIGURE 1 is a sectional view of the apparatus of the present invention.

FIGURE 2 is a sectional view of a modification of the closure plug forthe apparatus of the present invention.

FIGURE 3 is a sectional view of a modified head for the apparatus of thepresent invention.

FIGURE 4 is a sectional view of an electron beam gun for use in theapparatus of the present invention.

FIGURE 5 is a sectional view of a modification of the electron beam gun.

FIGURE 6 is a sectional view of another modification of the electronbeam gun.

For the purpose of illustrating the invention there is shown in thedrawings forms which are presently preferred, it being understood,however, that this inventoion is not limited to the precise arrangementsand instrumentalities shown.

One feature of the invention relates to the provision of a carrier platewhich is movable with respect to but has one surface in sealedconnection with the evacuated system enclosing the operative electronbeam, such plate being provided with a port therethrough adapted toreceive the workpiece in sealed manner therein and which can be movedfrom a vacuum-free loading position to an operative position in registerwith the electron beam by movement of the carrier plate over one or morepumping ports by which the space between the workpiece and said sealedsurface can be evacuated before the port registers with the beamposition.

One embodiment of this feature of the invention is shown in FIGURE .1 ofthe attached drawing where the carrier plate is in the form of a metaldisc 10 rotatable about a central stud 11 secured in a metal block 12.This block 12 carries an O-ring seal or similar gasket member 13adjacent its peripheral edge and a further O-ring of like seal 14 aroundthe stud 11. The continuously pumped electron beam system, indicatedschematically 3,222,496 Patented Dec. 7, 1965 only at 15, is sealed tothe block 12 with its mean beam axis x at a chosen distance r from theaxis of the stud 11. A further O-ring or like seal 16 surrounds anaperture 17 in the block 12, said aperture forming a continuation of theevacuated space of the system 15 while at a position diametricallyopposite the aperture 17 and at the same radial distance r the block 12is provided with a relief port 18 leading through valve 28 toatmosphere. This port is also surrounded by an O-ring or like seal 19. Apumping port 27 through the block 12 is connected to a source of vacuum,e.g., that associated with the system 15.

The disc 10 is provided, again at the same radial distance r from theaxis of the stud 11 with a port-likeaperture 20 shaped to provide a thinand narrow shelf 21 for reeciving the workpiece 22 in the form of ametal film carried upon the underside of a glass disc substrate. Abovesuch workpiece receiving zone a shoulder surface 23 carries an O-ring orlike seal 24 for sealing a closure disc or plug 25. The upper end of thestud 11 is conveniently screw-threaded and provided with a clamping nut26.

In the operation of this embodiment, the narrow space between theopposing surfaces of the disc 10 and block 12 confined within theperipheral seal 13 and limited also by the further seals 14, i6 and 19,is continuously pumped through port 27. With the disc 10 rotated throughto bring the aperture 20 in register with the relief port 18, theworkpiece 22 is inserted in position and the plug 25 secured and sealedin position. The disc 10 is then rotated through '180" to bring suchaperture 20 into register with the beam system 15. The valve 28 ismeanwhile closed so that immediately the small space beneath theworkpiece 22 becomes in fluid communication with the small volume andcontinuously pumped space between the disc 1t? and block 12, suchworkpiece space is also evacuated and when it reaches the position ofthe system 15 causes substantially no change in the vacuum level of thelatter. Working of the metal film of the workpiece, e.g., cutting ofsuch film, may take place without any appreciable delay, for instance,within 5 to 10 seconds. To enhance the security of the vacuum, theclamping nut 26 may be tightened during the Working phase. Removal ofthe workpiece is efiected by return of the aperture 20 to its initialposition in register with the relief port 18 and then opening valve 28followed by removal of the plug 25 and replacement of the finishedworkpiece by a fresh workpiece. If desired, the disc 10 may be providedwith a, preferably even, number of equi-spaced apertures 20 so that acontinuous How of workpieces to and from the working zone may beachieved.

Another feature of the invention relates to the provision of means forheating the metal component of the workpiece and/or the substrate uponwhich it may be carried to an elevated temperature close to that of theoperating temperature arising during the working phase, either justbefore or more preferably during the actual working phase.

One arrangement by which this may be achieved is illustrated in FIGURE 2of the drawing where an electric heater 30 of any suitable form isincorporated within the closure plug 25' so as to lie closely adjacentthe back of the workpiece 22 during the working operation.

By raising the temperature of the substrate and/ or the metal film ofthe workpiece to within, say 200 C. of

the melting point of the metal film, the energy required from the beamto effect cutting is substantially reduced thereby permitting the use ofa lower current density in the beam with accompanying easing of theproblem of obtaining a fine focussing of the beam to a spot of verysmall size. In addition, the workpiece is fully annealed after thecutting operation and the risk of fracture or crazing of the substrateis reduced or even avoided. The rate of cooling of the workpiece mayobviously be controlled by regulation of the energy supplied to theheater 30.

Deflection of the electron beam to perform, for example, cutting of themetal film of the workpiece, may be effected by beam deflection platesor other means forming part of the system 15. Alternatively, the beamdeflection system may be incorporated within a separate andinterchangeable head as shown at 311 in FIG- URE 3 which is adapted tofit into and be sealed in the aperture 20 of the disc instead of theclosure plug 25 of FIGURE 1. The workpiece 22 is now mounted in anequivalent aperture a at the upper end of the head 31. and sealed bysimilar means including a closure plug 25a and a seal ring 23a. The beamdeflection means are indicated schematically at 33. Heating means forraising the temperature of the workpiece may also be incorporated insuch interchangeable head 31. Difierent heads may be used to accommodatedifferent forms and sizes of workpiece.

Yet another feature of the invention relates to the provision of asharply focussed electron beam by the use of an emitting cathode of verysmall cross sectional area in a plane normal to the beam direction.

One example of improved cathode construction is shown in FIGURE 4 andhas the form of a small tungsten tube of, say, 0.001" internal diameterclosed at one end and provided upon its inner surface with suitableoxide or other emissive coating 36. Such tube is arranged to be heatedby means of an external heater winding 37 whereby the emitted electronsare directed axially out of the open end of the bore of the tube in avery small cross-section beam. To assist in confining the beam theheater may be surrounded by a negatively polarised shield or grid 38,While a positively charged anode 39 with a small diameter centralaperture 40 may likewise be used to accelerate and control the focussingof the electron beam.

An alternative example of cathode construction is shown in FIGURE 5where, instead of providing a separate heater winding, the internallycoated cathode tube is constructed as a helix 43 of flat metal strip,heating being effected by passing a suitable direct currenttherethrough, the positive terminal of the heating source beingconnected to the end of the cathode helix lying nearest the anode 39.

Yet a further example of cathode construction is shown in FIGURE 6 andtakes the form of a straight length of tungsten wire 46 arranged to liecoincident with the beam axis. This wire is provided with a heating coil47 there around at a position slightly spaced from the end lying nearestthe anode 39. The Wire cathode is arranged to be heated by means of theheating coil 47 to a temperature whereby its tip 48 is within theemitting temperature range; thereafter a boost in temperature isobtained at the tip by means of ion bombardment either from a separateanode 49 or by means of the main beam current. The heater winding ispreferably surrounded by a negatively charged shield. 50 and 39 indicaterespectively the normal grid and anode electrodes. To enhance the degreeof ion bombardment a slow leak of suitable gas, say, hydrogen, may bearranged to occur in the vicinity of the cathode tip 48.

In yet another arrangement according to the invention, the electron gunof the system 15 is designed in the form of a linear accelerator withsuch accelerator constructed as a tube resistive material having a highresistivity. For example, the tube may have a diameter of less than 1millimetre, a length of about 4 centimetres and a wall thickness of theorder of 0.5 millimetre. Such tube then acts to collimate the electronbeam and produces a uniform voltage gradient. The accelerating voltageis applied across the ends of the tube and by suitable graduation of theresistive value of the tube material along the tube length, the voltagegradient can be made to follow a prescribed law to enable a controlledbeam velocity to be obtained.

Such an accelerator tube may be made with magnetic properties forinstance, of a suitable ferrite, such that, with a suitably positionedcoil, a magnetic lens effect can be obtained at one or both ends of thetube in order to shape the cross-section of the electron beam. Theapplied magnetic field may be of a value below that producing saturationin the accelerator tube whereby the field inside the tube is at aminimum or alternatively the applied field may be above the saturationlevel of the tube material so that a field is produced inside the tubeto shape the beam while it is being accelerated thereby to confine thebeam to a minimum cross-section.

In experimental constructions ferrite tubes of the order of size quotedabove and with overall resistance values of between 400 and 1000 megohmshave been successfully used in conjunction with normal magnetic and/orelectrostatic focussing systems.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential attributes thereof, andaccordingly, reference should be made to the appended claims, ratherthan to the foregoing specification as indicating the scope of theinvention.

I claim:

1. Apparatus for working materials by means of an electron guncomprising a base disc; a carrier plate extending across and slightlyspaced from a surface of said base disc; means rotably supporting saidcarrier plate on said base disc; first sealing means between theadjacent surface of said base disc and carrier plate, said first sealingmeans extending completely around the base disc adjacent to but spacedfrom the edge of the base disc; said base disc having an electron gunreceiving aperture and a relief port extending therethrough, saidelectron gun receiving aperture and said relief port being equallyspaced from the axis of rotation of said carrier plate and opening, intothe space between the base disc and carrier plate within said firstsealing means; a second sealing means between the adjacent surfaces ofsaid base disc and carrier plate, said second sealing means surroundingthe electron gun receiving aperture; a third sealing means between theadjacent surfaces of the base disc and carrier plate, said third sealingmeans surrounding the relief port; said base disc having a pumping portextending therethrough and opening into the space between the base discand carrier plate within said first sealing means and outside of saidsecond and third sealing means, said pumping port adapted to beconnected to means for reducing the pressure in the space between thebase disc and carrier plate which is inside said first sealing means andoutside of said second and third sealing means; said carrier platehaving an aperture therethrough spaced from the axis of rotation of saidcarrier plate a distance equal to the spacing of each of the electrongun receiving aperture and the relief port from said axis of rotation,means in said carrier plate aperture for supporting the material to beworked; and a closure plug removably mounted across said carrier plateaperture; said carrier plate being rotatable with respect to said basedisc between a first position in which the carrier plate aperture isover the electron gun receiving aperture and a second position in whichthe carrier plate aperture is over the relief port.

2. Apparatus in accordance with claim 1 in which the means rotatablysupporting the carrier plate on the base disc comprises a stud securedto said base disc and extending through said carrier plate, said carrierplate being rotatable on said stud, a nut threaded on the end of saidstud which projects from said carrier plate and engaging the carrierplate to secure the carrier plate over the base disc, and sealing meansbetween the adjacent surface of the base disc and carrier plate aroundsaid stud.

3. Apparatus in accordance with claim 1 in which the means forsupporting the material to be worked includes a cylindrical headremovably mounted at one end in the carrier plate aperture, means insaid head for deflecting the beam of an electron gun, means in said headfor supporting the material to be worked, and the closure plug isremovably mounted across the other end of said head.

4. Apparatus in accordance with claim 1 including an electric heaterwithin the closure plug.

References Cited by the Examiner UNITED STATES PATENTS Krause 250-495Peters et al. 250-4l.9 Rommerts 25049.5

Dehn 31382 Levin 31382 Burdg 25041.9 Barber 219121 Radtke 219-121RICHARD M. WOOD, Primary Examiner.

JOSEPH V. TRUHE, Examiner.

1. APPARATUS FOR WORKING MATERIALS BY MEANS OF AN ELECTRON GUNCOMPRISING A BASE DISC; A CARRIER PLATE EXTENDING ACROSS AND SLIGHTLYSPACED FROM A SURFACE OF SAID BASE DISC; MEANS ROTABLY SUPPORTING SAIDCARRIER SEAL ON SAID BASE DISC; FIRST SEALING MEANS BETWEEN THE ADJACENTSURFACE OF SAID BASE DISC AND CARRIER PLATE, SAID FIRST SEALING MEANSEXTENDING COMPLETELY AROUND THE BASE DISC ADJACENT TO BUT SPACED FROMTHE EDGE OF THE BASE DISC; SAID BASE DISC HAVING AN ELECTRON GUNRECEIVING APERTURE AND A RELIEF PORT EXTENDING THERETHROUGH, SAIDELECTRON GUN RECEIVING APERTURE AND SAID RELIEF PORT BEING EQUALLYSPACED FROM THE AXIS OF ROTATION OF SAID CARRIER PLATE AND OPENING, INTOTHE SPACE BETWEEN THE BASE DISC AND CARRIER PLATE WITHIN SAID FIRSTSEALING MEANS; A SECOND SEALING MEANS BETWEEN THE ADJACENT SURFACES OFSAID BASE DISC AND CARRIER PLATE, SAID SECOND SEALING MEANS SURROUNDINGTHE ELECTRON GUN RECEIVING APERTURE; A THIRD SEALING MEANS BETWEEN THEADJACENT SURFACES OF THE BASE DISC AND CARRIER PLATE, SAID THIRD SEALINGMEANS SURROUNDING THE RELIEF PORT; SAID BASE PLATE DISC HAVING A PUMPINGPORT EXTENDING THERETHROUGH AND OPENING INTO THE SPACE BETWEEN THE BASEDISC AND CARRIER PLATE WITHIN SAID FIRST SEALING MEANS AND OUTSIDE OFSAID SECOND AND THIRD SEALING MEANS, SAID PUMPING PORT ADAPTED TO BECONNECTED TO MEANS FOR REDUCING THE PRESSURE IN THE SPACE BETWEEN THEBASE DISC AND CARRIER PLATE WHICH IS INSIDE FIRST SEALING MEANS ANDOUTSIDE OF SAID SECOND AND THIRD SEALING MEANS; SAID CARRIER PLATEHAVING AN APERTURE THERETHROUGH SPACED FROM THE AXIS OF ROTATION OF SAIDCARRIER PLATE A DISTANCE EQUAL TO THE SPACING OF EACH OF THE ELECTRONGUN RECEIVING APERTURE AND THE RELIEF PORT FROM SAID AXIS OF ROTATION,MEANS IN SAID CARRIER PLATE APERTURE FOR SUPPORTING THE MATERIAL TO BEWORKED; AND A CLOSURE PLUG REMOVABLY MOUNTED ACROSS SAID CARRIER PLATEAPERTURE: SAID CARRIER PLATE BEING ROTATABLE WITH RESPECT TO SAID BASEDISC BETWEEN A FIRST POSITION IN WHICH THE CARRIER PLATE APERTURE ISOVER THE ELECTRON GUN RECEIVING APERTURE AND A SECOND POSITION IN WHICHTHE CARRIER PLATE APERTURE IS OVER THE RELIEF PORT.